1. Field of the Invention
This invention relates to a process for purifying dinitriles containing chloride impurities. More specifically the process of this invention relates to a process for the purification of adiponitrile containing chloride impurities by treatment with high boiling amines.
2. Prior Art
Dinitriles are prepared by a variety of processes, for example, adiponitrile (ADN) from butadiene. One process involves the hydrocyanation of butadiene to form adiponitrile. Another process involves the chlorination of butadiene followed by treatment with a cyanide compound and hydrogenation to form adiponitrile. The crude adiponitrile prepared by such known processes is distilled to purify the adiponitrile. The purified adiponitrile can be used to prepare hexamethylene diamine which is used in the preparation of nylon. However, the adiponitrile may contain chloride impurities which adversely affect the hydrogenation catalyst activity for the preparation of hexamethylene diamine. Removal of the chloride impurities is desirable but said removal by distillation of the adiponitrile is very difficult and very expensive. U.S. Pat. No. 2,570,794 involves the separation of chlorine-containing impurities from organic nitriles by heating in the presence of benzene, water and trimethylamine or triethylamine. However, the addition of any compounds that would distill with the ADN would be very undesirable since high purity ADN is required for most applications. Thus not only do the chloride impurities adversely affect the hydrogenation catalyst activity in the preparation of hexamethylene diamine but the presence of any compound used to overcome this problem in the ADN in even small amounts will adversely affect the purity and yield of ADN.